Experts say they may have the answer for an “unprecedented” rise in wild mushroom poisonings that have been observed across California.
Since November 2025 there have been 47 cases of severe poisonings and four deaths reported statewide, according to the Napa County Public Health Officer.
“Recent rains have contributed to the resurgence of poisonous wild mushrooms in California, including in Napa,” said Dr Christine Wu. “Poisonous mushrooms can look and taste similar to safe mushrooms, and even experienced mushroom hunters have been affected by this outbreak.”
Wu’s warning comes after three adults were hospitalized over the weekend after eating poisonous wild mushrooms foraged in the Deer Park area, in Napa County. But she notes poisonous mushrooms can be found anywhere.
The two fungi types causing the illness are the Death Cap and Western Destroying Angel mushrooms, according to the California Department of Public Health.
The mushrooms in this outbreak have a group of toxins called amatoxins, which can cause severe damage to the liver and death in the most serious cases, according to Craig Smollin, medical director of the San Francisco Division of the California Poison Control System.
Symptoms of mushroom poisoning sometimes do not appear until up to 24 hours after a person eats them, and can cause nausea, vomiting, diarrhea and cramping.
Poisonous mushrooms can also resemble those that can be bought in grocery stores. The CDPH warns that those who arrive in California and are accustomed to foraging in their home countries face “serious risk” of mistaking them for mushrooms that are safe to eat.
Smollin, who also works at U.C. San Francisco, told SFGATE that California typically sees around five cases of poisoning per year on average.
“These cases are a continuation of a mushroom poisoning outbreak that began in November and is continuing for longer than usual. It is also unusually large and widespread,” he told the outlet, also noting the increased rainfall.
“It’s possible that allowed for another crop of these mushrooms to come up. It’s not unheard of that these mushrooms can grow year-round, not just during the rainy season,” Smollin said.
The best way of guarding against possible poisoning is simply to not eat wild mushrooms, the CDPH says.
In addition the agency advises parents to watch where children are playing closely, especially in areas where wild mushrooms grow. Pets should also be kept away from such areas, as animals can also be poisoned by mushrooms.
Cooking, boiling, freezing or drying poisonous mushrooms does not make them safe to eat, according to the CDPH.
